Long Beach Island Long Beach Island

Long Beach Island
Beach-Dune Susceptibility Assessment
Development and Applications
Coastal Research Center Facility
Great Bay…
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Dr. Stewart Farrell
Founder & Director
• Public Research and Services Center at Richard
Stockton College
Who
Who We
We Are...
Are...
• Originated in 1981 to assist local municipalities
with coastal issues
• Community Outreach Program
•
Coastal Zone Surveying and Monitoring
•
Established and Maintain Over 100 Sites Along the
Jersey Shore
•
Assessment of Coastal Features and Structures
•
Coastal Zone Management Related Activities
•
Federal, State, and Local Governments
•
Private Sector
•
Non-Profits
What
What We
We Do...
Do...
Who
Who We
We Work
Work For...
For...
Overview of Beach-Dune System Susceptibility Assessment
• Assess “performance potential” of oceanfront beach-dune system
•
•
•
•
Geospatial (GIS-based)
Expert knowledge used to integrate multiple variables (fuzzy-set theory)
Identifies weaknesses in the beach-dune system
Highlights areas susceptible to storm-induced damage
• Erosion and potential overwash or breach areas
• Foredune sand volume change
• Generates a GIS “susceptibility map”
• Development & Applications…
• “Alpha” - Holgate, NJ, Fall of 2002
• Proof-of-concept study
• Susceptibility relative to other dunes in the assessment area
• “Beta” - Mantoloking, NJ, Fall of 2004
• Dune toe recession used to control variable integration
• Susceptibility calibrated to storm intensities
• Regional-scale pilot assessment - Northern Ocean County, NJ (Spring 2007)
• NJ Statewide assessment - Sandy Hook to Cape May (just underway)
Observations
““The
The Real World
”
World”
Data
Processing
& Analysis
The
DecisionMaking
Process
Policy
Actions
Standards
Legislation
DecisionMaking
Interpretations
Information
Susceptibility of the Beach-Dune System
• Surveying & Mapping
…
Mapping…
••
••
••
Beach
Beach Erosion
Erosion Observations
Observations (seasonal
(seasonal &
& annual
annual “beach
“beach walks”)
walks”)
Shore
Shore Zone
Zone Surveying
Surveying (dune-beach-nearshore
(dune-beach-nearshore profiles)
profiles) &
& Field
Field Mapping
Mapping
LIDAR
LIDAR and
and Other
Other Remote-Sensing
Remote-Sensing Techniques
Techniques
• Analysis &
…
& Simulation
Simulation…
••
••
••
••
••
Trends
Trends in
in Long-Term
Long-Term Monitoring
Monitoring Data
Data (regression
(regression analyses,
analyses, etc.)
etc.)
Change-Mapping
Change-Mapping (time-slicing
(time-slicing historical
historical aerial
aerial images,
images, LIDAR)
LIDAR)
Spatial-Temporal
Spatial-Temporal Process
Process Modeling
Modeling
Time-series,
Time-series, Wavelets,
Wavelets, Fourier,
Fourier, etc.
etc.
Deterministic
Deterministic Numerical
Numerical Simulations
Simulations (SBEACH,
(SBEACH, EDune,
EDune, CHAMPS,
CHAMPS, others)
others)
• Geospatial Modeling
…
Modeling…
••
••
••
Identify
Identify Datasets
Datasets &
& Derive
Derive Variables
Variables Useful
Useful for
for Determining
Determining Susceptibility
Susceptibility
Weight
Weight the
the Importance
Importance of
of Variables
Variables
Integrate
Integrate Variables…
Variables…
•• Create
Create Map
Map Showing
Showing Levels
Levels of
of Susceptibility
Susceptibility
Surveying & Mapping
…
Mapping…
New Jersey Beach Profiling Network
•• Established
Established in
in 1986
1986 in
in Response
Response to
to Hurricane
Hurricane Gloria
Gloria (1984)
(1984)
•• 100
100 Beach
Beach Profile
Profile Sites
Sites
•• At
At least
least 11 Site
Site in
in Every
Every Oceanfront
Oceanfront Municipality
Municipality
•• 77 Sites
Sites Located
Located in
in the
the Lower
Lower Delaware
Delaware &
& Raritan
Raritan Bays
Bays
•• Topographic/Bathymetric
Topographic/Bathymetric Survey
Survey from
from Backdune
Backdune to
to -16ft
-16ft Depth
Depth
Design and Considerations
•• At
At least
least 11 profile
profile site
site in
in each
each community
community
•• Use
Use existing/previous
existing/previous survey
survey locations
locations
•• Avoid
Avoid proximity
proximity to
to groins
groins or
or inlet
inlet jetties
jetties
•• Bracket
Bracket tidal
tidal inlets
inlets with
with aa survey
survey site
site
•• Start
Start survey
survey profile
profile behind
behind dune
dune or
or other
other shore
shore
protection
feature
protection feature
•• Survey
Survey each
each Fall
Fall (also
(also Spring
Spring since
since 1994)
1994)
•• Emergency
Emergency surveys
surveys following
following
declarations
declarations
•• Survey
Survey natural
natural areas
areas
Federal
Federal disaster
disaster
•• Survey
Survey sandy
sandy shorelines
shorelines in
in Delaware
Delaware &
& Raritan
Raritan bays
bays
Surveying & Mapping
…
Mapping…
Surveying & Mapping
…
Mapping…
Beach Profile Survey Equipment
CDMA
&
RTK
GPS
“Total-Station”
Laser Survey
Transit
Survey
Rods,
Radio,
Flags
Surveying & Mapping
…
Mapping…
NJBPN Near shore bathymetric surveys
•Provide cross-sectional beach profiles
run cross-shore, from the landward
extent of the dune to the near shore zone
(beyond the extent of LiDAR elevation
data).
•Used in the creation of near shore and
beach-dune surfaces used in the BeachDune susceptibility assessment
Data Processing, Analysis, &
Profile Calculation
Analysis & Simulation…
• LIght Detection And Ranging (LIDAR)
Similar to RADAR (RAdio Detection And Ranging)
• Collects broad, densely spaced, highly accurate elevation data
• NOAA, USGS, NASA, Universities, and numerous private contractors
• Shoreline Change,
Coastal and
Erosion
Monitoring…
Analysis & Simulation…
• LiDAR data, combined with photogrammetry allows for creation of baseline datasets
to perform delineations
•
•
•
•
Dune Crest
Landward and Seaward Dune Toes
Shoreline
10 ft. Waterline
LiDAR Point Distribution
LiDAR Extracted Dune Delineations
Analysis & Simulation…
Rapid Analysis Generated from LIDAR
Little Egg Inlet
439 Bins, Equal-Interval, 250-Foot Wide
FEMA 540-Rule
3D dune crest elevation line
Barnegat Inlet
Analysis & Simulation…
• The GIS-based beach-dune assessment integrates several geospatial datasets into weights of
susceptibility within zonal analysis areas call “bins”
• Bins run long-shore parallel
to shoreline
• Each bin divides the beach
into 250-foot sections
• Within each zonal analysis
bin, geospatial calculations
are performed to extract
beach-dune characteristics
based on base data such as
LiDAR elevation data and
Photogrammetric data.
Bins are also used to symbolize various beach-dune attributes
Analysis & Simulation…
Digital Elevation Model (DEM) created using LiDAR data
Surf City, Long Beach Island
“Raw”, Unprocessed
LIDAR Point Elevations
Digital Elevation Model
Analysis & Simulation…
Vegetation Classification
Field mapping & verification
of dune vegetation…
Dune vegetation and in-dune structures extracted
from infrared aerial photography using image
processing techniques…
Analysis & Simulation…
Other Geospatial Datasets Derived from LiDAR Data
Slope
Dune
Dune Area
Area
Elevation
Dune
Dune Width
Width
Crest-Axis
Profile
LBI – HarveyDune
Cedars
Dune Crest
-Axis Profile
LIDAR Elevation Data From Fall of 2000
(looking from a boat at the beach, from the south to the north)
30
South of Eastward St.
To South of Atlantic St.
25
S. of 68
To
N. of 73
22 ft >
Feet (NAVD88)
20
15
Dune Height Statistics
10
18.0 ft
25.9 ft
13.2 ft
12.7 ft
Examples of isolated
dune crest low areas
(typically street ends)
5
Average
Maximum
Minimum
Range
0
0
2000
Southern Boundary...
4000
6000
Feet from Southern Borough Boundary
8000
10000
…Northern Boundary
Geospatial Modeling
Fundamental Methods
• Data-Driven
• Statistical approach
• Model parameters & weighting calculated from training sites
• Weights of evidence, weighted logistic regression, neural networks, fractal
methods
• Knowledge-Driven
• Expert system approach
• Model parameters & weighting estimated by expert(s)
• Boolean logic, index-overlay, process models, Fuzzy logic, Dempster-Shafer
belief theory
• All Models are Wrong…
• But they provide insight
• Only a tool to facilitate analysis, not replace the expert
Geospatial Modeling
Basic Approach
Raw
Datasets
Maps
Weighting
Map of Correlation, Suitability,
Favorability, Probability, Susceptibility, etc.
Optimize
The
“ Model ”
Integration
Geospatial Modeling
Beach
-Dune Susceptibility
Beach-Dune
Susceptibility Modeling
Modeling
Geospatial Modeling
Weighting
Weighting of
of Beach-Dune
Beach-Dune System
System Attributes
Attributes
Variables Calculated on a
Per Bin Basis
•Average Dune-Crest Elevations
Values
Values Normalized
Normalized Between
Between 00 and
and 11
•Dune Width
•Beach Width
Values Combined Together
•Percent Vegetation Coverage
•Presence of Groins
•Foredune Slope
Weighted
Weighted Susceptibility
Susceptibility Value
Value
Per
Per Bin
Bin
Analysis & Simulation…
• LiDAR generated profiles combined with a U.S Army Corps storm simulation
model CEDAS (Storm-induced BEAch CHange) SBEACH …
• Simulates 2D beach profiles for 2-year, 5-year, 10-year, 20-year, 50-year storm events using
Federal Emergency Management Association (FEMA) based storm parameters
• SBEACH storm simulations provide…
• Dune recession analysis
• Volume change analysis
• Dune breach vulnerability points
Analysis & Simulation…
• Pre
-Storm profile
Pre-Storm
• Post
-Storm (50 year storm) profile
Post-Storm
SBEACH Pre and post storm profile output
Geospatial Modeling
Linking Susceptibility to Modeled Storm Event Intensity
• SBEACH (Storm-induced BEAch CHange)
• USACE Coastal & Hydraulics Lab
• Numerical simulation of cross-shore beach change
• Intended to predict short-term beach profile response to
storms
Recession of Dune Toe
Nearly to Dune Crest for 20-Year Storm
---year storm
--- 50
50-year
storm event
event
---year storm
--- 20
20-year
storm event
event
---year storm
--- 10
10-year
storm event
event
Lower
In Relation to Storm Intensities with
Respect to Dune Toe Recession
Higher
Dune
Dune Crest
Crest Breached
Breached
Geospatial Modeling
Digital
Digital Elevation
Elevation Model
Model made
made from
from LiDAR
LiDAR year
year 2005.
2005.
High
High and
and wide
wide dune
dune system
system
The beach-dune susceptibility
assessment highlights areas of low and
high susceptibility. Illustrated in the
top right image are two contrasting
regions located within a mile radius.
The digital elevation model used in all
of the images depicts areas of higher
elevation with warmer colors (reds)
and areas of low elevation with cooler
colors (blues).
20 yr Storm Susceptibility Strip
Low
Low and
and narrow
narrow dune
dune system
system
Geospatial Modeling
20 yr Storm Susceptibility Strip
During
During aa storm
storm event
event
Low
Low and
and narrow
narrow dune
dune system
system of
of Merivale
Merivale Avenue
Avenue
Geospatial Modeling
Wide beaches at Tebco Avenue,
Holgate NJ
The susceptibility model predicts that this
region of Holgate will provide adequate
protection against a 20-year storm event.
Good sloping, highly vegetated dune system
Geospatial Modeling
Barnegat Light Borough Dune System
Barnegat Light Borough has undoubtedly the strongest natural
dune systems on Long Beach Island. It is one of the only regions
which meets the FEMA 540 front dune volume.
Natural
Natural Dune
Dune System
System in
in Barnegat
Barnegat Light
Light
Geospatial Modeling
The FEMA 540-rule definition states:
"primary frontal dunes will not be
considered as effective barriers to base
flood storm surges and associated wave
action where the cross-sectional area of the
primary frontal dune, as measured
perpendicular to the shoreline and above
the 100-year stillwater flood elevation and
seaward of the dune crest, is equal to, or
less than, 540 square feet."
FEMA 540-Rule: Frontal Dune, Average
Cross-Sectional Area
Dune Toe Recession
Past Dune Crest…
Slump Blocks, Just Short of Dune Crest,
Formed by Undercutting
• What it is…
• An assessment to identify weaknesses in the beach-dune system…
• Areas where some degree of erosion or failure is likely to occur
• An analysis of natural and anthropogenic dune-related features…
• Dune height, width, slope, vegetation, etc.
• Sand-fencing, sand-retaining structures, dune modification, etc.
• A synthesis of multiple datasets that vary in character and size on spatial scales at
least as small as a property block
• Performed within discrete spatial zones (“bins”) along beach-dune system length
• What it is Not…
• Not a probability model…
• Does not provide a probability of dune erosion, overwash, breach…
• Does not predict effects of damage due to dune erosion, overwash, or failure
• Not a wave impact / dune erosion simulation
• Not a long- or short-term shoreline change/evolution model
• Not comprehensive…
• Does not take into account sand volumes (yet) and other variables
• Not a means of determining insurance rates, pricing real estate, predicting
structural damage, etc.